1. Field of the Invention
The present invention relates to a chlorine-containing resin composition which produces extremely a small amount of hydrogen chloride at fire disasters or at combustion.
2. Brief Description of the Prior Art
As usual, chlorine-containing resin compositions such as polyvinyl chloride as a typical example are universally used synthetic resins having a large amount of production, widely used for wire insulating, hose, sheet, film for agricultural use, bottles, construction materials including those for floors, walls and waved plates, or pipes, because of their low cost, excellent workability and free selectability over the range of hard to soft properties.
Polyvinyl chloride is featured in that, as containing chlorine, it exhibits high flame resistance. In other word, hydrogen chloride (hereinafter referred to HCl) produced at combustion of polyvinyl chloride suspends oxygen which is needed at combustion to exhibit flame resistance. However, HCl itself is a harmful and moreover corrosive gas, which is harmful to the human body especially at fire disasters. In addition, it is also one of the causing material of the recent acidic rain. Also, there is another problem that, when the municipal disposals are processed, the furnace wall is damaged due to corrosive property of HCl.
Although polyvinyl chloride is a largely useful material at being processed or in use, the limitation of its use has been proposed, since it produces HCl at combustion. Nevertheless, chlorine (Cl) necessary for producing polyvinyl chloride is an inevitable by-product produced at the process of electrolysis of NaCl (sodium chloride) for producing Na (sodium) as an industrially fundamental material, and one of important uses of Cl is especially suited for polyvinyl chloride. Therefore, the tendency of producing polyvinyl chloride in order to effectively consume Cl produced in manufacturing Na cannot be easily changed.
Accordingly, the important problem is how to deal with the harmful HCl generated in combustion of polyvinyl chloride. If it is enabled to decrease the quantity of produced hydrogen chloride as few as possible, it can be said the problem is solved. In other words, if no or extremely small amount of HCl is produced even when polyvinyl chloride is combusted, the balance between the quantities of Na and Cl produced as by-product in the soda industry would not be lost, and therefore polyvinyl chloride is evaluated as a useful and harmless resin. Moreover, polyvinyl chloride contains about 60% of chlorine by weight, consumes petroleum less than any other resins, and accordingly can be again recognized as a very useful resin for humans.
Recently, a flame retardant such as antimony trioxide is added in order to effect flame resistance of polyvinyl chloride, but there is a problem of relative effect with the produced HCl and detriment of HCl is still maintained, and toxicity of antimony trioxide also cannot be overlooked.
Further, for the reason of toxicity of the flame retardant, some of non-toxic hydroxides such as aluminum hydroxide or magnesium hydroxide are attempted to be used. The use of these flame retardants would cause polyvinyl chloride to be flame resistant by way of water produced through the process of dehydration. However, although polyvinyl chloride can be caused to be flame resistant up to about 300 degree C, such a property of polyvinyl chloride is not already maintained where the surface of the flammable substance is raised in the range of 700 to 800 degree C. In addition, the quantity of HCl produced at combustion even added with the flame retardant is almost the same as compared with that without the flame retardant, and still harmful nature of HCl is not reduced.
In addition, as an agent for uptaking HCl generated on combustion of the typical resin, that is polyvinyl chloride, any of calcium compounds such as calcium carbonate, especially of finely ground type thereof, calcium hydroxide, or calcium oxide is preferable, and calcium carbonate is used in practice.
Furthermore, the repeated experiments performed by the inventor over the long period of time have proved the following matters. Previously, uptaking ability of calcium compounds for HCl has been determined through the combustion test in the range from 500 to 600 degree C, which is, however, not appropriate, because the surface temperature of a substance in the actual combustion process reaches 700 to 800 degree C.
The inventor has performed a burning test of the conventional HCl uptaking compound, such as calcium compound, especially on calcium carbonate, up to the high temperature ranging from 750 to 800 degree C. The result has proved that, although such a compound has exhibited a relatively high grade of uptaking ability for HCl in the range of 500 to 600 degree C, the uptaking ability has reduced to the grade of about 50% at the higher temperature of about 800 degree C. The reason therefor is assumed that CaCl.sub.2, produced by the reaction with Cl contained in polyvinyl chloride, undergoes hydrolysis by the water contained in the air flowing during combustion, and, as a result, releases chlorine which the CaCl.sub.2 once captures.
The assumption above can be also supported by the following documents Nos. 1, 2 and 3 as reference:
1. Hiroshi Kubota, Shigeo Uchida, and Kaneru Kanaya: "A Fundamental Study of Hydrogen Chloride produced from Sodium Chloride", Study Report (1), June 1980, Plastics Treatment Promoting Society; PA1 2. Hiroshi Kubota, Shigeo Uchida et al: "On Volatile Chlorine contained in Municipal Garbage"; City and Waste, Vol. 112, No.8; PA1 3. Shigeo Uchida: Production and Removal of Hydrogen Chloride in the Trash Burner", Separation Technology, 22.4, 1992. PA1 (1) a chlorine-containing resin composition including, a chlorine-containing resin, and at least one selected from the group consisting of lithium hydroxide, lithium hydroxide monohydrate and lithium carbonate; PA1 (2) a chlorine-containing resin composition including, a chlorine-containing resin, at least one selected from the group consisting of lithium hydroxide, lithium hydroxide monohydrate and lithium carbonate, and calcium carbonate; PA1 (3) a chlorine-containing resin composition including, a chlorine-containing resin and lithium carbonate having a particle size of not exceeding 20 micron m, preferably not exceeding 10 micron m; PA1 (4) a chlorine-containing resin composition including, a chlorine-containing resin and lithium carbonate having a particle size of not exceeding 20 micron m, preferably not exceeding 10 micron m; admixed with at least one selected from the group consisting of metallic soaps of Zn, Cd and Pb; PA1 (5) a chlorine-containing resin composition including, a chlorine-containing resin and lithium carbonate having a particle size of not exceeding 20 micron m, preferably not exceeding 10 micron m; admixed with at least one selected from the group consisting of metallic soaps of Zn, Cd and Pb, and at least one selected from the group consisting of an epoxy compound, a phosphorous ester, a beta-diketone, a polyol, a carboxylic acid, and a salt of lithium carboxylate; and PA1 (6) a resin molded product comprising one of chlorine-containing resin compositions according to one of the forgoing 1 to 5, as the principal starting material.
Also, another possibility is assumed that the evaporated CaCl.sub.2 can be hydrolyzed by the water vapor, since such water vapor can be contained in the entering air and CaCl.sub.2 is melted and liquidized owing to the temperature raised, over its melting point of 772 degree C. Also, in the case of any other calcium compounds, although Ca is reacted with Cl and CaCl.sub.2 is formed, CaCl.sub.2 is hydrolyzed to release Cl. Therefore, even though the uptaking ability is high enough in the temperature range of 500 to 600 degree C (middle temperature range), it is lowered in the high temperature range of about 800 degree C. Hence, calcium compounds are not said to exhibit high HCl uptaking ability in the high temperature range, since it is hydrolyzed to release HCl.
Tests, which have been performed on the compounds of alkali metals and alkali earth metals, have proved that each of compounds of sodium (Na), magnesium(Mg) and potassium (K) which can produce NaCl, MgCl.sub.2 and KCl, respectively, is effective as a HCl uptaking agent. However, the sodium compounds, when blended with chlorine-containing resin, is not satisfactory in HCl uptaking ability, and further the produced NaCl is hydrolyzed at 800 degree C. In the case of Mg compounds, the produced MgCl.sub.2 is thermally decomposed even in the relatively low temperature range below 500 degree C. In the case of potassium compounds, which exhibit deliquescence, it is not suitable as the filler, and, hydrolyzed at high temperature, also is not suitable for a HCl uptaking agent. Thus, it is proved still difficult to uptake HCl by use of each chloride of alkali metals and alkali earth metals, because each of them is hydrolyzed at high temperature.